深紫外發光二極體（波長≤290 nm）在目前的設計中通常選用P型結構來提高導電性。然而，P型結構中鎂離子的摻雜會形成中間能階(位於價電帶邊界上方約 150~220 meV )，此能階會吸收量子井中載子複合後所產生的紫外光，降低元件的發光效率。因此，我們致力於開發一種以未摻雜的GaN和高品質的AlN結構形成的二維電洞氣(2-dimensional hole gas, 2DHG)來實現高導電、高穿透的性能。利用二維電洞氣，我們能解決使用P型結構中摻雜鎂離子所引起的吸光問題。同時，由於二維電洞氣之磊晶層的厚度相對傳統P型結構更薄，更能減緩P型磊晶層的吸光問題，達成高紫外光穿透的目標。
在本研究中，我們利用一維 drift-diffusion charge control solver (1D DDCC) 軟體進行能帶模擬。從模擬結果中觀察到，在15 nm的GaN磊晶覆蓋層厚度下，AlGaN量子井表面的電洞濃度可達最大值9.7×1020 cm-3。本研究使用有機金屬化學氣相沉積法成長GaN/AlN磊晶層，希望得到高品質的二維電洞氣。我們以兩吋c-plane藍寶石為基板，先成長一層AlN，再成長GaN。透過磊晶時間來調整GaN磊晶層的厚度，並分析不同厚度的GaN對於磊晶品質和元件電性的影響。未來，我們將持續優化二維電洞氣的磊晶條件，以提高磊晶品質，並將其應用於DUV LED結構，以提升發光效率。

Deep ultraviolet light-emitting diodes (DUV LEDs, wavelength ≤ 290 nm) typically utilize a p-type contact layer to control the current spreading and light extraction efficiency. However, doping with magnesium acceptors in the p-type layer creates impurity levels (150~220 meV above the valence band), which absorb the ultraviolet light generated by carrier recombination in the quantum well. Therefore, we are devoted to developing a two-dimensional hole gas (2DHG) formed by undoped GaN and high-quality AlN structures to achieve high conductivity and high transparency. Using the 2DHG, we can overcome the light absorption issues caused by impurity levels. Additionally, the thin (< 30 nm) epitaxial layer of 2DHG can minimize the UV absorption.
In this study, we conducted simulations using a one-dimensional drift-diffusion charge control (DDCC) solver. From the simulation results, it was observed that the hole concentration reached a maximum value of 9.7×1020 cm-3 at the GaN capping layer thickness of 15 nm on the AlGaN quantum wells. To grow high-quality 2DHG, we employed metal-organic chemical vapor deposition (MOCVD) and 2-inch c-plane sapphire substrates. We aim to form the 2DHG by the interface of GaN/AlN. The epitaxial thickness of GaN was controlled by adjusting the growth time, and the effect of GaN layer thicknesses on epitaxial quality and device electrical properties was investigated.

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